I apologise if this has been asked before. I did do a search but only came up with uses of the word, not explanations of what it means. Allow me to explain:

I've been reading through a lot of these threads and quite often, in combination with split ends, I've seen people talking about "dusting". I have quite a few split ends, and no money to go to a hair dresser/stylist. I've recently decided I need to start taking better care of myself and my hair and I'd like to know what "dusting" is, how it's done and what the benefits are? If it matters, my hair is at least mid-back and very straight and fine, although I've been told I have a lot of hair.

Thanks in advance.

Dusting is where you will trim off the damaged ends and splits, but only trim off those ends.  It can be a little tedious, and very time consuming, but well worth it.  It is really important to only use good sharp hair cutting scissors when doing this, or you are likely to cause more damage.  

The methods that I've seen a lot are to take small sections of hair, twist gently and cut the ends that stick out and are split.   I generally just start trimming splits that are sticking out from my braid.  

also be carefull to trim off the damaged ends right across (i mean really hold your scissors perpendicular to the strand of hair. and i use always the tips of the scissors to cut, it's usually the sharpest and it's way more accurate. i don't only look for split ends but also "white dots", this is the beginning of a split end or a place a hair broke off. in my opinion regular dusting is an absolute must, not only you remove all split ends in the first phase but if you keep doing it regular you also prevent new ones by cutting of very small damage (this requires way less triming, like just 2 mm). every end that looks weird to me (hair shaft exposed, white dots) are cut.
i don't use the twisting technique, i prefer to jujst take a strand and watch over the whole length for strange ends  8)

It's a chore but I do it when I have time to kill like when I am waiting in the car or waiting for someone, gives me something constructive to do when I would otherwise be doing nothing.  ;)

I never dust, I just do search and destroy, which is looking through your hair to find splits and breaks, then trimming them out one by one.

Endless entertainment.

Me too... search and destroy. I don't dust because it apparently doesn't give any improvement like it used to ... (and also because it became a very addictive and hindering hobby ;D )